Computer Memory Terms

BGA (Ball Grid Array) - A chip package having solder balls on the underside for mounting. BGA allows for a reduction in die package size, better heat dissipation, and greater module densities.

Chip-Scale Package (CSP) - Thin chip packaging whereby electrical connections are typically through a ball grid array. Chip-scale packaging is used in RDRAM and flash memory.

DDR (Double Data Rate Memory) - The latest generation of SDRAM technology. Data is read on both the rising and the falling edge of the computer clock, thereby delivering twice the bandwidth of standard SDRAM. With DDR SDRAM, memory speed doubles without increasing the clock frequency.

DIMM (Dual In-line Memory Module) - A printed circuit board with gold contacts and memory devices. A DIMM is similar to a SIMM, but with this primary difference: unlike the metal leads on either side of a SIMM, which are "tied together" electrically, the leads on either side of a DIMM are electrically independent.

DRAM (Dynamic Random-Access Memory) - The most common form of RAM. DRAM can hold data for only a short time. To retain data, DRAM must be refreshed periodically. If the cell is not refreshed, the data disappear.

Megabyte (MB) - The most common term used to denote the capacity of a memory module. 1 megabyte equals approximately one million bytes, or exactly 1 byte x 1,0242 (1,048,576) bytes.

Memory - A computer's random-access memory. Memory temporarily holds data and instructions for the CPU. Also referred to as memory module. See RAM.

Memory Bank - A logical unit of memory in a computer, the size of which the CPU determines. For example, a 32-bit CPU requires memory banks that provide 32 bits of information at a time. A bank can consist of one or more memory modules.

Micro BGA (µBGA) - Tessera, Inc. BGA chip packaging technique that allows for a reduction in die package size, improved heat dissipation, and greater module densities.

MicroDIMM (Micro Dual In-Line Memory Module) - Smaller than an SODIMM, MicroDIMMs are primarily used in sub-notebook computers. MicroDimms are available in 144-pin SDRAM (up to 133MHz from Kingston) and 172-pin DDR (up to 333MHz from Kingston).

Motherboard - Also known as the logic board, main board, or computer board, the motherboard is the computer's main board and in most cases holds all CPU, memory, and I/O functions or has expansion slots for them.

RAM (Random-Access Memory) - A memory cell configuration that holds data for processing by a central processing unit (CPU). Random means the CPU can retrieve data from any address within RAM. Also see Memory.

RIMM™ (Memory Module) - The trademarked name for a Direct Rambus memory module. A RIMM™ conforms to the DIMM form factor and transfers data 16 bits at a time.

SDRAM (Synchronous DRAM) - A DRAM technology that uses a clock to synchronize signal input and output on a memory chip. The clock is coordinated with the CPU clock so the timing of the memory chips and the timing of the CPU are in synch. Synchronous DRAM saves time in executing commands and transmitting data, thereby increasing the overall performance of the computer. SDRAM allows the CPU to access memory approximately 25 percent faster than EDO memory.

SODIMM (Small-Outline Dual In-line Memory Module) - An enhanced version of a standard DIMM, as they are smaller and thinner than a DIMM and are used primarily in notebook computers. A 72-pin small-outline DIMM is about half the length of a 72-pin SIMM. 144-pin and 200-pin modules are the most common SODIMMs today.

TSOP (Thin Small-Outline Package) - A DRAM package that uses gull-wing leads on both sides. TSOP DRAM mounts directly on the surface of the printed circuit board. The TSOP package is one-third the thickness of an SOJ. TSOP components commonly occur in small-outline DIMMs.